Danh sách liên kết vòng

// Danh sach lien ket don vong.

#include<iostream>
using namespace std;
int n;
struct Node{
int data;
Node *next;// chua dia chi node ke tiep ma no tro toi
};

struct List{
Node *head;
Node *tail;
};

void Init(List &l){ // k tao List rong
l.head = l.tail = NULL;
}

Node *creatNode(int x ){ //tao thong tin cho node
Node *p = new Node;
if(p == NULL) exit(1);
p->next = NULL;
p->data = x;
return p;
}

bool isEmpty(List l ){ // k tr a xem lieu List co rong hay k.
if(l.head == NULL ) return true;
return false;
}

// chen vao dau List:
void addHead(List &l, int x ){
Node *p = creatNode(x);
if(isEmpty(l)) l.head = l.tail = p;
else{
p->next = l.head; // con tro next cua p tro toi dia chi cua node head(ban dau)
l.head = p; // cap nhat node head( luc sau )
}
l.tail->next = l.head; // khep vong don.
}
// ham chen vao cuoi List
void addTail(List &l, int x ){
Node *p = creatNode(x);
if(isEmpty(l)) addHead(l,x);
else{
l.tail->next = p;
l.tail = p;
}
l.tail->next = l.head; // khep vong don
}
// tim kiem
Node *search(List l, int k ){
Node *p = l.head;
do {
if( p->data == k ) return p;
else p = p->next;
} while( p != l.head );
return NULL;
}

void addMid(List &l, int x, int k ){ // chen node co data = x vao sau node co data  = k;
Node *p = search(l,k);
if(p!=NULL){
Node *q= creatNode(x);
Node *r = p->next;
p->next = q;
q->next = r;
}
else cout<<"\nKhong tim thay node co data = k.";
}
/*
void addAtK(List &l, int x, int k ){ // chen vi tri bat ki;
if(isEmpty(l) || k<= 1 ) addHead(l,x);
else if(k>= n) addTail(l,x);
else{
Node *p = creatNode(x);
Node *q = new Node, *w = new Node;
Node *r = l.head;
int dem = 0;
while(r!=NULL){
dem++;
q = r;
if(dem == k ) break;
else r = r->next;
}
w = l.head;
while(w->next!= q) w = w->next;
w->next = p;
p->next = r;
}
} */
// nhap vao mot list bat ki
void nhap(List &l){
cout<<"\nnhap so ptu ban dau cua List: "; cin>> n;
for(int i = 1; i<= n; i++ ) addTail(l,i);
}
// xuat thong tin ra man hinh
void xuat(List l ){
if(l.head){
cout<< "\nDanh sach cac phan tu: \n";
Node *p = l.head;
do{
cout<<" " << p->data;
p = p->next;
}while( p != l.head );
}
else cout<< "\nDanh Sach Rong";
cout<< endl;
}

void delHead(List &l ){ // xoa node o dau List
if(!isEmpty(l)){
if(l.head != l.tail ){
Node *p = l.head;
l.head = l.head->next; // cap nhat l.head
delete p; // xoa bo node head ban dau
l.tail->next = l.head;
}
else l.head = NULL;
}
else return;
}

void delTail(List &l ){
if(!isEmpty(l)){
if(l.head != l.tail ){
Node *p = l.head;
Node *q = new Node;
while(p->next != l.tail ) p = p->next; // tim node ngay truoc tail
q = p; // gan node nay cho node q
p = p->next; // p chinh la node tail can xoa
l.tail = q; // cap nhat l.tail
l.tail->next = l.head;
delete p;
} else l.head = NULL;
}
else return;
}

void delAtK(List &l, int k ){
if( k <= 1) delHead(l);
else if( k >= n ) delTail(l);
else{
int dem = 0;
if(!isEmpty(l)){
Node *p = l.head;
Node *q = new Node;
while(p != NULL){ // tim node thu k.
dem++;
q = p;
if(dem == k ) break; // tim thay thi break
else p= p->next; // k thi tim tiep
}
Node *r = l.head;
while(r->next != q ) r = r->next; // tim node k-1
r->next = q->next; // cho node next cua node k-1 tro toi node k+1;
delete q;
}
}
}

void menu(){
List l;
Init(l);
nhap(l);
xuat(l);
int k, x, lc;
do{
cout<<"\n______MENU______\n1_Chen dau.\n2_chen cuoi."
<<"\n3_Chen sau vi tri node data = k.\n4_Chen vao vi tri bat ki."
<<"\n5_Xuat Thong tin List.\n6_Xoa phan tu dau List."
<<"\n7_Xoa phan tu o cuoi List.\n8_Xoa node o vi tri k."
// <<"\n9_Sap xep QuickSort."
<<"\n0_Thoat.\n_Ban chon ? ";
cin>> lc;
switch(lc){
case 0: break;
case 1: cout<<"\nNhap x: "; cin>> x; addHead(l,x); n++; break;
case 2: cout<<"\nNhap x: "; cin>> x; addTail(l,x); n++; break;
case 3: cout<<"\nNhap x, k: "; cin>> x >> k; addMid(l,x, k);n++; break;
// case 4: cout<<"\nNhap x, vi tri k: "; cin>> x >> k; addAtK(l,x,k); n++; break;
case 5: xuat(l); break;
case 6: delHead(l); n--; break;
case 7: delTail(l); n--; break;
case 8: cout<<"\nNhap vi tri k: "; cin>> k; delAtK(l,k); n--; break;
// case 9: QuickSort(l); break;
}
}while(lc != 0 );
}

int main(){
menu();
return 0;
}